CURITABA, Brazil  Huge nature reserves that stretch across national frontiers are being formed in Asia, South America and elsewhere, a sign that biodiversity has joined security and immigration as a border issue.

More than a dozen countries at the 8th U.N. conference on the Convention on Biodiversity in Brazil this week agreed to set up transnational parks or linked national parks in the jungles of Borneo, the steppes of Central Asia and the Pacific Ocean islands of Micronesia.

In the Amazon rain forest, half a dozen governments are working to create up to four nature reserves.

"This is one of the most exciting things we are seeing -- very large scale initiatives by countries to create networks of protected areas," James Leape, director general of the global conservation group World Wildlife Fund, told Reuters.

Dozens of countries have agreed to meet a U.N. goal to slow the pace of biodiversity loss by 2010. Extinctions are now more numerous than at any time since dinosaurs roamed the Earth.

But many countries rich in biodiversity lack money. Government officials at the conference have lobbied environmental groups, corporations and the United Nations to help pay for managing the parks and protecting them from poachers.

Border parks have existed for years along the U.S.-Canada frontier but they are not as immense as the reserves now being created.

In Borneo, a biodiversity hot spot that holds 6 percent of the world's species of plants and animals and where 361 species were discovered in the last decade, the governments of Brunei, Indonesia and Malaysia hope to stem deforestation by doubling a protected area to 84,950 square miles, an area nearly the size of Britain.

"This represents a very significant milestone for transboundary cooperation," said Dato Suboh, secretary general of the Malaysian environment ministry.

SILK ROAD RESERVE

In the Caucasus Mountains of Central Asia, near the ancient Silk Road trade route, five nations with histories of political instability and ethnic conflict -- Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan, Turkmenistan -- have agreed to set aside 44 percent of their collective geography, or some 695,000 square miles, by linking national parks and creating new wildlife corridors to protect their deserts, high mountain meadows and tundra.

The sparsely populated rugged areas would be nearly the size of Mexico.

Efforts in the Amazon are also under way to link South American national parks, state parks and Indian reservations, though presidential elections scheduled for this year in many of the countries are causing delays.

Biologists are working on a reserve for the border region of Peru, Bolivia and Brazil, another linking Suriname, French Guiana and Brazil, a third linking Brazil with Venezuela and a fourth linking Brazil with Colombia.

In the Pacific, the Republic of Palau, the Federated States of Micronesia, the Republic of the Marshall Islands, the Commonwealth of the Northern Mariana Islands and the U.S. Territory of Guam are raising funds to set aside up to 30 percent of their marine territory and 20 percent of their lands to preserve fish stocks and terrestrial species.

Island nations are urgently trying to protect biodiversity because they may be most acutely affected by global warming that bleaches the fish stock incubators of sensitive coral reefs and causes sea levels to rise.